The present invention relates to an optical recording/reproducing apparatus for recording an information signal such as a video signal on a disc-like recording medium as a format of a change in optical characteristic of a material of the medium or reproducing the recorded information signal from the recording medium and, more particularly, to an apparatus having an overlap recording preventing circuit for preventing that in the case of recording an information signal on the medium by such an apparatus, this information is overlappingly recorded in the portion on the medium where the information has already been recorded.
In an optical recording/reproducing apparatus, in general, a disc-like recording medium is used and an information signal is recorded as spiral or coaxial recording loci on the disc or reproduced therefrom.
The disc having coaxial recording loci is suitable for recording and reproducing still image information. On the other hand, the disc having spiral recording loci (hereinafter, referred to as tracks) is suited to record and reproduce continuous signals such as a video signal of an animation or the like and audio signals or the like.
Although an information signal can be easily continuously recorded on the spiral tracks, it is necessary to take measures to prevent a new information signal from being overlappingly recorded on the portion where the information signal has already been recorded in the case where information is recorded on the track sections of a few turns and the recording is once interrupted and thereafter the recording of new information is restarted or where an additional signal is newly recorded on a plurality of track sections on the recording medium on which the information signal has already been recorded, or the like. One track section denotes the portion of one turn of the tracks.
As measures to prevent such overlap recording, for example, there has been known an apparatus shown in the Official Gazette of Japanese Patent Unexamined Publication No. 147141/82. This apparatus intends to first detect reproduced RF (radio frequency) signals from a plurality of objective track sections on which an information signal is recorded. When no reproduced RF signal is detected, those track sections are determined to be the sections where no signal is recorded and the information signal is recorded on those track sections.
The conventional apparatus as shown in this Official Gazette detects the final ends of the recorded track sections; therefore, in the case where the number of recorded track sections is large, it takes a long time to check them.